Iowa HVAC Radon Mitigation Requirements

Why HVAC Contractors Need to Know About Radon

Iowa consistently ranks among the highest radon states in the country — the EPA estimates that about 70% of Iowa homes have radon levels above the 4 pCi/L action threshold. That background level is why the legislature passed House File 2297, which directly affects new residential construction and the HVAC contractors working on those builds.

What HF 2297 Requires

House File 2297 directs the Department of Inspections, Appeals, and Licensing (DIAL) to amend the state building code to mandate passive radon mitigation systems in all newly constructed single-family or two-family homes. The requirement applies to construction that commences after the formal adoption of the amended rules by the State Building Code Commissioner.

A passive radon system typically includes:

• A gas-permeable layer beneath the foundation slab
• A vent pipe routed from beneath the slab through the building envelope to above the roofline
• Sealed penetrations at the slab level to prevent soil gas entry
• A rough-in for a future fan installation (converting passive to active mitigation if needed)

The system doesn't require power or mechanical components in its passive form — it relies on natural convection to vent soil gases.

How This Intersects with HVAC Work

HVAC contractors on new residential builds need to coordinate with the radon mitigation system in several ways:

Duct routing: The radon vent pipe needs a clear vertical path from the slab to the roofline. On projects where you're designing the duct layout, account for the radon pipe's location early. A vent pipe that can't run vertically because ductwork blocks its path creates a change-order situation.

Sealed slab penetrations: Coordinate any penetration through the basement slab for condensate lines, refrigerant lines, or gas piping with the radon system design, and seal it as required by the applicable code. Unsealed penetrations around HVAC equipment can become preferential pathways for soil gas.

Return air considerations: In basements and crawl spaces, the HVAC return air system can create negative pressure that draws radon-laden soil gas into the living space. Properly balanced duct systems with adequate outdoor air intake help prevent this — a consideration during Manual J and Manual D calculations.

Licensing for Radon Work Itself

The HF 2297 requirement concerns the passive system in new residential construction; it does not establish that an HVAC license authorizes active radon-mitigation work. Confirm the applicable Iowa requirements before taking on active mitigation work.

An HVAC contractor's role on this requirement is to coordinate with the building team; before installing a radon system, confirm the applicable Iowa requirements and refer active work to a certified radon mitigator when required.

What Inspectors Will Check

On new construction, local building departments enforce the adopted building code and may inspect the passive radon system before related work is concealed. Confirm the local inspection sequence. For HVAC contractors, the inspection points that overlap with your work include:

• Slab penetrations are properly sealed
• HVAC ductwork doesn't obstruct the radon vent pipe route
• Mechanical room layout accommodates the radon vent pipe

The Iowa HVAC License Guide covers the full scope of new construction requirements for HVAC contractors — including permit sequencing, inspection coordination, and code references for the 2024 International Mechanical Code.

See more Iowa guides →